Piezoelectric speakers are widely used as simple electroacoustic conversion means in earphones, headphones, and other acoustic devices, and speakers for mobile information terminals, for example. For instance, Patent Literature 1 discloses a piezoelectric speaker constituted by a piezoelectric element joined to a vibration plate made of metal material.
Also, recent acoustic devices include hybrid electroacoustic transducers. For instance, Patent Literature 2 discloses a complex speaker combining a dynamic speaker (electromagnetic sounding body) and a piezoelectric speaker (piezoelectric sounding body).